I would advise making the “unleaded”, “Diesel”, “Premium” options RadioButtons instead of Buttons and bind them under a container like Panel. So, when the user presses the “buttonTotal” the program will check which RadioButton is checked and then calculate the corresponding value.
private void btnTotal_Click(object sender, EventArgs e)
{
double totalPrice = 0;
if(unleadedRadioButton.Checked)
{
totalPrice = lblDailyPrice * lblTotalLitresEntered * unleadedValue;
}
else if (dieselRadioButton.Checked)
{
totalPrice = lblDailyPrice * lblTotalLitresEntered * dieselValue;
}
else if (premiumRadioButton.Checked)
{
totalPrice = lblDailyPrice * lblTotalLitresEntered * premiumValue;
}
}